Base foreign-chain request support in mpc-SDK

[DSharifi]

Background

When supporting foreign chain validation requests for the Base chain, we should also extend the near-mpc-sdk crate's functionality to also create foreign chain validation requests to the Base chain.

User Story

As a user of the near-mpc-sdk I want to be able to construct foreign chain validation requests for the Base chain.

Acceptance Criteria

The near-mpc-sdk crate is able to create requests and verify Base foreign chain requests

Resources & Additional Notes

No response